Thursday, February 24, 2011

Killer wasps are coming! (to the 28th annual Insect Fear Film Festival)

Killer wasps are coming! (to the 28th annual Insect Fear Film Festival)

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In anticipation of the 28th Annual Insect Fear Film Festival, which they will host Saturday on the U of I campus, this week’s Environmental Almanac is written and narrated by four members of the Entomology Graduate Student Association: Michelle Duennes, Rob Mitchell, Laura Steele and Katherine Noble.

[Katherine] This year's festival, Killer Wasps, plays on our almost primal fears of these stinging insects. However, the majority of wasps can't sting people, and actually don't care much about us at all. Most wasps are parasitoids, which means their larvae live inside other insects. Many others are herbivores and feed on plant material. Only a small subset of social wasps have evolved to be the stinging predators with which we're most familiar. [The wasp pictured here, Isodontia mexicana, is native to Illinois. It may look fierce, but its sharp ovipositor is used to lay eggs in the larvae of other insects, not to sting people. Photo by Alex Wild,]

[Rob M.] The first wasps were almost certainly herbivores that fed on leaves or inside the wood of trees. Many of these species are still around today, and you might know them as sawflies or wood wasps. They appear quite different from other wasps: the larvae look almost exactly like caterpillars, and the adults lack the characteristic "wasp waist." Though most are small and unremarkable, a local species called the horntail can reach lengths of up to an inch and half. Horntails are so named from the stiff, powerful spine extending from their abdomen called an ovipositor, which they use to chisel into wood and lay eggs. Even if you have never seen a horntail, you may come across its horn embedded in a tree after the luckless insect was snatched by a bird while laying eggs.

[Laura] The majority of wasps are parasites or parasitoids. Parasites exploit a host for reproduction or development purposes without killing the it, while parasitoids ultimately kill the organism that hosts their larval development.

The unlucky insect host of a parasitoid often remains alive, either paralyzed or unable to remove the invading larva, while it is essentially eaten from the inside. While this may be a living nightmare for the host insect, it can be a miracle for farmers, who often use parasitoids to help control insect pests of crops.

The smallest known insect, the fairy fly, is actually a tiny parasitoid wasp that has a wingspan of about 3 millimeters or less. On the other extreme is the large Cicada Killer wasp, which can be one-and-a-half inches in length. Here in Illinois, you are likely to see one of these wasps dragging a paralyzed cicada into its underground burrow where it will then lay an egg on the immobile insect.

[Michelle] At some point, most of us have been stung by some sort of wasp or bee. Stingers are modified ovipositors, which means that only female bees and wasps are capable of stinging. Like bees, some wasps possess a form of sociality, which is when individuals of the same species live together, share resources and divide labor and reproduction among the individuals in the group. Unlike the honey bee, wasp colonies can have multiple egg-laying females, called gynes.

The social wasps include the insects most people know as hornets, yellowjackets, and paper wasps. One of the more infamous stinging wasps is the velvet ant or cow killer. Its sting is incredibly painful, but it can’t actually kill cows.

The Insect Fear Film Festival will take place at the Foellinger Auditorium on the UI campus, with festivities beginning at 6:00 p.m. and films beginning at 7:00. Further details are available at